A rotary hammerbreaker including a plurality of discs driven upon a rotor shaft, a plurality of rods extending through the discs parallel to the rotor shaft and radially spaced therefrom and a plurality of hammers pivotably mounted upon the rods between the discs. The hammerbreaker is provided with a protective device consisting of a plurality of shields each including a hub mounted upon one of the rods between adjacent discs. The shields are formed with a circular segmental flange fixed to the hub extending over a part of the periphery of each of the adjacent discs between which the hub is mounted to protect the disc periphery. The flange has a circumferentially extending portion which is an integral fraction of a whole circle so that a number of the shields can be fitted to a rotary hammerbreaker to provide substantially continuous protection around the periphery of the discs.